(Since the perimeter is the length of each sides added up. Two sides are equal to x+6 and two are equal to x-6)
2 (x+6) + 2 (x-6) = 48
(break out the brackets)
2x + 12 + 2x -12 = 48
( 12 and -12 cancel out and "disappear".)
2x + 2x = 48
4x = 48
(Rearrange for x)
x = 48 / 4
x = 12 inches
Feel free to ask if you have any questions
